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  Apple Inc. has started an iPhone trade-in program in its stores, letting owners sell older handsets back to the company in exchange for credit toward a new model.  Apple’s U.S. retail outlets are now accepting devices, said Amy Bessette, a spokeswoman for Apple. The initiative is starting just before the next iPhone’s debut on Sept. 10. While Gazelle Inc. and wireless carriers such as Verizon Wireless and AT&T Inc. already buy used handsets, this is the first program run by the iPhone maker at its stores. By buying old phones, they’re aiming to spur new device sales by helping cover the cost of buying the latest smartphone. Apple is teaming up with Brightstar Corp., a mobile-phone distributor, to run the operation, people with knowledge of the plans said in June. “IPhones hold great value so Apple Retail Stores are launching a new program to assist customers who wish to bring in their previous-generation iPhone for reuse or recycling,” Bessette said. “In addition to he...

This is  Interview question that every PLC programmer came across in his carrier.The Question is very tricky and shows the fundamentals (basic Ladder Laws) and depth of candidates knowledge. Today we are going to discuss PLC program for Push to ON device  and Push to Off Device.But the trick is that we have to use  only Normally open(NO) ,Normally Close (NC) contacts ,and Coil as output only(No timer,Counter, OSR ). In short there will be a single Push Button Input (X0) , and one Output (Y0). When user press Push button for 1st time output will be ON ,when user Presses Push Button for 2nd time output will be OFF. This is also called as "Push to On Push to Off " logic.Analogy can be provided with "TV" on and off Push Button.    We Can Break Sequence Like This : 1) Push Button Pressed (X0) ==> Output (Y0)On 2)Push Button Released (X0)==> Output (Y0) Latched 3)Push Button Pressed (X0)==> Output (Y0 )Off 4)Push Button Released (X0)==> Output (Y0) O...